1. Field of the Invention
This invention relates to wiper blades. More particularly, but not essentially, the invention relates to wiper blades for wiping surfaces of changing curvature, e.g. windscreens of vehicles whether a motor car, aeroplane, train or ship. However, the wiper blades are also applicable in other industries, for example the printing and food industries for wiping surfaces, and can be used for wiping surfaces which are curved or flat.
The invention also relates to spring elements and to articles including such spring elements.
2. Prior Art
Wiper blades of the type used for cleaning windscreens comprise a wiping blade, usually made as an extrusion or moulding of rubber or other resilient material, and a carrier for the wiping blade. It is important that the wiper blade conforms to the changing curvature of the windscreen surface through its movement range and to this end known carriers provide a multi-point mounting system for holding the wiping blade in a manner which allows the blade to change its curvature as it wipes over the windscreen surface. Most known carrier assemblies comprise a plurality of arcuate spring fingers or rockers pivoted intermediate their ends, which ends provide contact points with further fingers or rockers or with the wiping blade.
The known arrangement suffers from the disadvantage that there tend to be marked pressure points along the length of the wiping blade which can cause uneven wiping due to lower contact pressure between the blade and the windscreen at intermediate locations. Furthermore, the degree of curvature which can be accommodated by the known construction is limited and often results in lifting of the blade, especially at the ends where the screen is heavily curved.
A still further disadvantage of the known construction is that it utilises many components which have to be assembled together to form the carrier and then to which the wiping blade is fitted including a flexible metallic reinforcing strip for the wiping blade. Several components, often ten or more, are involved in a typical wiper blade and the time required for assembling them increases the cost of the wiper blade. Also, because of the number of components involved, the components of the wiper blade tend to freeze together in cold conditions, which restricts the ability of the wiper blade to conform to the change in curvature of the windscreen.